Electroacoustic resonators are of interest because, among other things, they can be used to perform signal processing and sensing functions. Electroacoustic resonators include surface acoustic wave (SAW) and bulk acoustic wave (BAW) resonators, as well as micromechanical resonators, or “microresonators”.
For example, microresonators fabricated from aluminum nitride (AlN) are used in radiofrequency (RF) filters, accelerometers, and sensors. AlN is one example of a piezoelectric material that responds both electrically and mechanically to applied electric signals, and that can be formed into an electroacoustic resonator capable of modifying such signals.
For any electroacoustic resonator-based filter, signal degradation can arise from undesired spurious responses. For instance, an AlN microresonator can be designed to efficiently transduce to any of various desired modes, but transduction to the numerous undesired symmetric and anti-symmetric Lamb modes, as well as interactions of acoustic waves with various device components, can also give rise to spurious responses. Accordingly, additional resonator architectures and methods are needed to reduce and mitigate such spurious responses.